weboob compat: override sys.meta_path to prevent package loaded twice

Use case: the core does "import woob.x" but some app does "import
weboob.x". This loaded modules twice and prevented isinstance() from
cooperating. This trick loads modules only once.

weboob/__init__.py

@@ -17,11 +17,43 @@
 # You should have received a copy of the GNU Lesser General Public License
 # along with woob. If not, see <http://www.gnu.org/licenses/>.
 
+import sys
+from importlib.abc import MetaPathFinder, Loader
+import importlib
+
 import woob
 
 
-__path__ = woob.__path__
 __title__ = woob.__title__
 __version__ = woob.__version__
 __author__ = woob.__author__
 __copyright__ = woob.__copyright__
+
+
+# Use case: the core does "import woob.x" but some app does "import weboob.x".
+# If we merely set __path__, python will generate different modules
+# though they have the same path. So the references will be different,
+# isinstance(woob.X(), weboob.X) will fail, etc.
+# Instead, we must return the same module to prevent Python from generating
+# another one.
+# Trick found at https://stackoverflow.com/a/56872393
+
+class AliasLoader(Loader):
+    def module_repr(self, module):
+        return repr(module)
+
+    def load_module(self, fullname):
+        new_name = fullname.replace("weboob", "woob")
+        module = importlib.import_module(new_name)
+        sys.modules[fullname] = module
+        return module
+
+
+class AliasImporter(MetaPathFinder):
+    def find_module(self, fullname, path=None):
+        root_name, _, __ = fullname.partition(".")
+        if root_name == "weboob":
+            return AliasLoader()
+
+
+sys.meta_path.append(AliasImporter())